The present invention is related to a rubber composition which imparts excellent adhesive property between a rubber composition and a reinforcing material when preparing a composite product of the rubber and the reinforcing material.
Heretofore, in forming a bond between a rubber and a metallic material such as steel cord or between a rubber and a fibrous material such as nylon cord, it has been known to plate the metal material with zinc or a copper alloy such as brass and bronze in the former case and to treat the fibrous material such as nylon cord with a resorcinol-formaldehyde latex in the latter case.
In order to improve the adhesive property, it has been known to add certain additive such as a cobalt salt of organic acid such as cobalt naphthenate, cobalt stearate, and cobalt octylate in the rubber.
However, the adhesive system has the disadvantages that the adhesive property is suddenly decreased by excess time or temperature of a heat treatment in a vulcanization and a moisture resistance of adhesion is low. In order to improve the adhesion, it has been proposed to add an alkyl-phenol resin to compensate for the decrease of adhesive property caused by the vulcanization.
In said case, it is hard to expect an improvement of moisture resistance and the vulcanization is disadvantageously slow.